The present invention relates to a new and improved high-voltage circuit breaker or switch.
The present invention relates specifically to a new and improved high-voltage circuit breaker comprising at least one primary switching position and an auxiliary switching position series connected with a cut-on resistor and connected in parallel to the primary switching position. A common drive rod is operatively coupled to both a first linkage transmission system leading to the primary switching position and to a second linkage transmission system comprising an actuator rod controlled at one end thereof by a follower or entrainment member cooperating with a cam and leading to the auxiliary switching position. Means are provided which during a cut-on stroke sequentially cause closing of the auxiliary switching position, then closing of the primary switching position and thereafter opening of the auxiliary switching position.
In a high-voltage circuit breaker as known, for example, from German Patent Publication No. 1,939,555, published Feb. 12, 1980, the cam has the shape of a segment-shaped cam disc which is rigidly non-rotatably mounted to a drive rod which is rotated in one rotational direction for the cut-on stroke and in the other rotational direction for the cut-off stroke. A follower member coupled to a movable switching member rolls upon the circumference of the cam disc. During a cut-on stroke the cam disc displaces the aforementioned switching member against the action of a spring into its cut-on position, retains the same in this position until immediately prior to the actual completion of the cut-on stroke of the circuit breaker and thereafter releases the follower member. The switching member of the auxiliary switching position then jumps back into its original position under the action of the spring which has been tensioned by the cut-on stroke.
It is a disadvantage inherent in this operational and functional concept that at the end of the jump-back of the switching member at the auxiliary switching position two stops impact against one another and the blow originating therefrom may with time be detrimental for different parts of the system, namely the movable members of the auxiliary switching position, not even taking into account wear. Additionally, the spring associated with the switching member at the auxiliary switching position must be tensioned during each cut-on stroke and the work required therefor must be exerted by the drive unit of the circuit breaker. Finally, it should be mentioned that it is in particular the contact breaking stroke occurring at the auxiliary switching position at the end of the cut-on stroke which is exclusively dependent upon the faultless functioning of the spring as well as upon the trouble-free displaceability of the switching member associated with the auxiliary switching position. In case that, for example, due to some deposits or contaminants the switching member sticks in the cut-on position or the spring breaks then the aforementioned functions are no longer ensured, i.e., the contact breaking stroke at the auxiliary switching position is not guaranteed to occur because this action neither is visible nor controllable from the outside.
Similar conditions prevail in a high-voltage circuit breaker as known, for example, from European Patent Publication No. 0,031,791, published July 8, 1981. Here the switching member at the auxiliary switching position is coupled by a connecting rod to a kind of crank drive. This crank drive comprises a disc which is mounted for rotation with a drive rod but is non-rotatable with respect thereto. The drive rod is rotatable or rockable back-and-forth through an angle of about 90.degree., and in the disc there is formed a circularly-shaped or arcuate cam track extending over an angle of about 90.degree. and arranged concentrically with respect to the drive rod. The cam track comprises a radially outwardly bent-off section at one of its ends and a rubber cushion or shock absorber at the other one of its ends. In the cut-off position the connecting rod extends over the drive rod and engages the bent-off section of the cam track by means of a follower or entrainment member placed at the end of the connecting rod located on the side of the drive. The switching member at the auxiliary switching position is biased into the cut-off position by means of a spring. Now when the cam track is rotated by the drive rod in a direction in which the bent-off section leads the cam track, then the switching member at the auxiliary switching position is advanced by the connecting rod and against the action of the spring into the contact-making or closed position, until the bent-off section of the cam track has arrived at such a position relative to the displacement direction of the switching member that the spring thereof can urge the follower member at the connecting rod out of the bent-off section. Thereafter the follower or entrainment member is abruptly displaced through the cam track under the action of the spring until abutting the rubber cushion at the other end. Simultaneously, the switching member at the auxiliary switching position performs the contact-breaking or opening stroke.
The observations previously made with reference to German Patent Publication No. 1,939,555 are here valid even to a greater extent. The contact-breaking or opening stroke at the auxiliary switching position only is ensured if the spring functions in a trouble-free manner, if the switching member is displaceable, and additionally if the follower member is freely displaceable in the cam track. Also in this case a spring must be tensioned during the cut-on stroke and, here too, the jump-back of the switching member at the auxiliary switching position generates shocks which are, however, somewhat attenuated by the rubber cushion or shock absorber.